The invention pertains to a method of making a water-soluble, polyvinylbenzyl quaternary ammonium halide by halomethylation of a cationically-initiated polystyrene and subsequent quaternization of the resulting halomethylated product.
Polyvinylbenzyl quaternary ammonium halides have been prepared by chloromethylation and subsequent quaternization of polystyrene or by chlorination of polyvinyltoluene and subsequent quaternization as described in Canadian Patent No. 640,156. The resultant quaternized products, however, appear to be less than about 50 percent quaternized. Moreover, as mentioned by G. D. Jones, Industrial and Engineering Chemistry, 44:2686 (1952), formation of insoluble gels occurs in the chloromethylation of polystyrene when carried to greater than about 75 mole percent, due to crosslinking, which renders such a product unfit for uses where the final product must be water-soluble, such as water clarification. Derivatives of polystyrene prepared by addition polymerization have an added drawback in that they have a yellowish or orangeish hue unless the polystyrene is subjected to hydrogenation, a separate procedure involving platinum or platium catalysts with the additional expense thereof.
A soluble, linear polyvinylbenzyl quaternary ammonium halide may be prepared according to the procedure of U.S. Pat. No. 2,780,604 by polymerizing a vinylbenzyl halide monomer and quaternizing the resultant product or by first quaternizing the monomer and thereafter polymerizing to obtain the soluble, linear polymer. The process described for preparing the vinylbenzyl halide monomer involves both halogenation and dehydrohalogenation steps. Possibly due to the relatively large expense involved, only one commercial source of the monomer in the U.S. is presently known to applicants.